Molecular dynamics simulations of void growth and coalescence in single crystal magnesium

Abstract

The growth and coalescence of voids in magnesium single crystals at the nanoscale have been investigated using molecular dynamics simulations and the embedded atom method. One void and two void specimens with identical initial void volume fractions were utilized to study the mechanism of void growth and coalescence. In order to study the influences of material length scale on void evolution in single crystals four specimen sizes with the same initial volume fraction of voids were considered. Investigations of the effects of temperature and strain rate were also performed. Uniaxial stress–strain curves were monitored during increasing employed strain. The simulation results show that the specimen size, loading strain rate and temperature had apparent influences on the twin or dislocation pattern, void evolution shape and uniaxial stress–strain responses, but negligible effects on the initial slopes of the uniaxial stress–strain curves. Furthermore, the nucleation stress of twin bands in orientation A – x[0 0 0 1]– y[ 1 2 ¯ 1 0 ]– z[ 1 0 1 ¯ 0 ] was much higher than that of plastic deformation in orientation B – x[ 1 2 ¯ 1 0 ]– y[ 1 0 1 ¯ 0 ]– z[0 0 0 1].